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28 July 2014

Below are the full instructions on how to build exactly what I built. There is so much that could be done to improve the design. I know it is not anywhere close to perfect. The materials I used were makeshift, whatever was lying around the house or wasn’t too expensive. But that was the point. I like spontaneity. It doesn’t have to be extremely elaborate to work and to be useful. This is for anyone who wants to do anything with it or for anyone who is just interested.

Methods
Building the device:
1. Two identical wooden rings were cut from the compressed fiber board using the reciprocating hand saw. The circumference measured at 2.5”, the thickness (which was just the thickness of the original board) at .5”, and the width of the ring at .5”.
2. Three identical holes on the cross sectional sides of each ring, 120 degrees apart were drilled.
3. Each ring was thickly coated with the Minwax varnish (for waterproofing) and then left to dry. (multiple coats were applied)
4. One ring was placed on either end of the three dowel rods (one through each of the drilled holes), yielding an open track for water to move through.
5. The three dowel rods were secured to the rings with the epoxy glue.
6. One proximity sensor was screwed horizontally onto the interior face of each ring, directly between two of the metal rods and directly opposite each other along the length of the track.
7. A thin layer of silicone sealant was applied directly to all surfaces of the sensors (for waterproofing.)
8. Each of the sensors had a long cord with two exposed wires sticking out at the end (one white and one black.) The two white wires (one from each sensor) were screwed into the 7 pin on the breakout board and the two black wires were screwed into the 8 pin.
9. The multi pronged wide end of the USB connector was then plugged into the Port on the breakout board. (the other end was later plugged into a computer which supplied the data.)
10. The electrical connection between the sensors cords, the breakout board, and the USB connector was then secured and partially protected with a wrapping of electrical tape. (to protect from water droplets, but NOT fully waterproof.)
11. Two small holes were drilled on each of the wooden rings, just above the magnetic sensors on the curved face of the ring.
12. Through each of these holes a tightly wound thread of 24 gauge twister was strung. (The tops of these wires were secured together with epoxy glue.)
13. Running the length of the track, the wooden slat was secured with electrical tape through the wound wire twister handles.
14. A nylon string was tied to either end of the wooden slat to be used as a device for lowering the system into the water.
15. The steel strip cut from a can was then tacked to a hard plastic foosball (about an inch in diameter); one end on one side of the ball and one end on the opposite side of the ball. This yielded a tall metal loop protruding above the original height of the ball on either side.
16. Two 1” sections of heavy plastic drinking straw were cut on one side each so that they could be slipped over and onto two of the steel rods.
17. Then, two pieces of straight coat hanger wire (about 2” long each) were set across the rails through the loop from one straw to the other and glued in place with silicone sealant to the top of the foosball (just below the loop.) This created a freely moving object for the track.

Taking the Data:
First, the speed of the stream was measured with the Vernier Flow Rate sensor. The speed was measured at approximately 60% of the depth. The Vernier Flow Rate sensor transmitted continuous data which was automatically stored in a graph on the Lab Quest data processor. (speed vs. time for 3 minutes each)
Secondly, the same procedure was with followed with the designed device which transmitted individual data points to an excel spreadsheet which was later compared with the Vernier data. The USB connected to the device was plugged into a computer and used through the Xnote stopwatch timer program. When the device entered the water the moving object was pushed from one end of the track to the other which sent a signal through the magnetic sensors to the timer program which measured the time it took for the ball to travel the length of the track. The speed was computed by dividing the length of the track by the time it took for the traveling object to move from one sensor to the other.
This experiment looked for a significant difference between the Vernier data and the experimental device’s data. Data was collected in two separate outings. On the first day, 50 speeds were computed with the designed device and 5, 3-minute, continuous runs of data were taken with the Vernier device. Then a design change was made to reduce friction (resulting in the device described earlier.) On a second day, 25 speeds were computed with the designed device and 3, 3- minute, continuous runs of data were taken with the Vernier device.

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Welcome

I'll be trying what seems to be an unusual approach in blogs -- writing to be inclusive of students in middle school and jr. high*, as well as teachers and parents (whether for their own information or to help their children). To that end, comments will have to pass a stricter standard than I'd apply for an all-comers site. It shouldn't be onerous, just keep to the topic and use clean language.

I expect it to be fun for all, however, as you really can get quite far in understanding the world, even climate, by understanding this sort of fundamental. If I get too much less fundamental, let me know where I went astray.

* Ok, I concede that not many middle school students will get everything. Even a fair number of adults will find some parts hard to follow. Still, some middle school kids will have fun. And almost everyone will follow a number of posts just fine.

Please see the comment policy for details. And the link policy for details about that. The latter is more open than you might expect.

About Me

In my day job I work on the oceanography, meteorology, climatology, glaciology end of my science interests, but I'm interested in everything, science or not. So I've also been on stage in a production of Comedy of Errors, run an ultramarathon, and been to Epidaurus, Greece, to see a production of Euripides' Iphigenia among the Taurians
Prior to starting the current job, I was a post-doc in oceanography in the UCAR ocean modelling program, and earned my doctorate from the Department of the Geophysical Sciences at the University of Chicago (1989). My undergraduate degree involved Applied Math, Engineering, Astrophysics, and Glaciology.
Of course I don't speak for my employer, whoever that may be.